1. Field of the Invention:
This invention relates to electrical apparatus and, more particularly, to high voltage switches.
2. Description of the Prior Art:
Switches for control of high voltage electricity are widely used by industry and electrical utilities. In a common design, the line terminals and separable contacts are at high potential and are supported by insulating columns, one of which is rotatable. Mechanical energy to operate the separable contacts is provided by a motor-drive and is transmitted to the contacts by means of a linkage coupled to the rotatable insulating column. Field conditions may require that a standard design switch have its motor-drive placed in any of a variety of positions. Means must therefore be provided for field assembly and adjustment of the coupling between the linkage and the rotatable insulating column.
In U.S. Pat. No. 1,905,784 there is described an adjustable operating lever for a high voltage switch which employs a lever with a semicircular clamp surface and a separable heel price cooperating with a polygonal shaft attached to a rotatable insulating column. However, positive positioning of the operating lever at a specific angle on the shaft is not provided by this lever. Another device used in the prior art is a two-piece assembly including a bolt circle in each piece, each circle of the same radius, with a large number of holes equally spaced in each circle. The pieces are placed in the desired relationship and bolted together. This method provides positive positioning, but to provide adjustment increments of, say, four degrees, it is necessary that 90 holes be placed in each bolt circle. In order for the bolt holes to be of adequate size, this method requires bolt circles of large radius and correspondingly large assembly members. This increases rotational inertia of the insulating column and slows switch operation. In addition, it is not always possible to assure a symmetrical pattern of connecting bolts, thereby introducing undesirable stress concentrations.
Another coupling method employs a shaft attached to the rotatable insulating column and extending through a lever with a toothed surface. The lever is positioned at the desired angle and clamped tightly against a cooperating toothed surface on the rotatable insulating column. The toothed surfaces are expensive, however, and require casting or machining.
Some mechanical linkages, such as that described in British Pat. No. 15,281 of 1902, have included methods providing a limited amount of adjustment, utilizing two series of equally spaced holes, the spacing of one series being unequal to the spacing of the other series. However, the mechanism taught by this patent also provides an asymmetrical bolt pattern. It would be desirable to provide a high voltage switch with an operating arm adjustable 360.degree. around a rotating insulator column with small adjustment increments, positive positioning, symmetrical bolt pattern, and of simple, lightweight, low-cost construction.